1. Field of the Invention
This invention relates to medical containers, and more particularly to medical containers such as blood bags and transfusion bags which are provided with a sheetlike joint and made of a vinyl chloride resin compound.
2. Description of Prior Arts
Medical containers such as blood bags and transfusion bags have heretofore been produced by piling two pre-cut sheets of a vinyl chloride resin compound one on top of the other and sealing their common edges by high-frequency heating. High fabricability, physiological safety, transparency, low cost and the like are main reasons for the choice of vinyl chloride resin compound as the material. In the case of the conventional vinyl chloride resin, the sealing by high-frequency heating has entailed the disadvantage that the sealed portions of sheets tend to sustain tears or pinholes when the temperature is too high and the joined faces of sheets tend to peel when the temperature is too low.
Generally concerning sheets of synthetic resins, it has been proposed to improve the heat sealing property by using sheets of dissimilar materials widely different in thermal resistance. This method, however, has proved impracticable with soft vinyl chloride resin because this resin shows poor fusibility with other resins and loses its flexibility when exposed to the conditions of lamination. The aforementiond medical containers such as blood bags and transfusion bags normally contain medicinal solutions such as anticoagulants and liquids for transfusion. The conventional containers made of vinyl chloride resin compound have suffered these medicinal solutions to be lost by evaporation because the resin has relatively high perviousness to steam.
It is, therefore, an object of this invention to provide novel medical containers. Another object of this invention is to provide medical containers which do not sustain tears and pinholes in the sealed portions when the sealing is effected by high-frequency heating. Yet another object of this invention is to provide containers made of a vinyl chloride resin of low previousness to steam and high flexibility and used for holding medicinal solutions.